As reported below, at the very end, maybe you can try narrowing the groove with side stock to make its width like tool's

Hope it helps, regards.

You can make a single plunge cut into a groove that is the same width as the tool insert.

To cut grooves equal to the insert width:

Place at least two containment trim planes (or points) around the groove feature as shown below. The containment trim planes can be aligned with the walls, or simply placed near the walls. This forces the grooving tool to cut into the narrow groove.

Containment trim planes aligned with groove wall

Containment trim planes placed near groove walls

Remove any positive operation stock.

Remove any positive custom boundary offsets or stock applied to the groove.

As the groove width equals the insert width, the tool will cut the groove.

Result:

or

Stock and boundary offsets

You can use this same technique to cut a groove that is equal to the insert width after applying stock and boundary offsets. Verify this equation applies: groove width – 2 * (stock+offsets) = insert width.